What is the difference between a product cost collector and production order?

Both of these are cost objects which collect production costs for
manufactured product. Product cost collector is a single order created for
a material. All the costs during the month for that material is debited to
single product cost collector. No costing by lot size is required in case of
product cost collector.

The latter is where there are many production orders for a single material
during the month. Costs are collected on each of this production order.
Costing by lot size is the main requirement in case of production orders.